the plesk import tool is in a very rough state and I am very busy at other projects so there is no real progress at the moment.
I used the tool to convert all of my customers including webs and emails from plesk to ispconfig but:
1.) i use ispconfig 3.0.5 beta (latest version from stable branch)
2.) i do not know what plesk version i imported from
The conversion worked, although i do not import dns entries.
Before using the importer script some settings have to be written into the plesk importer php file by hand (like mysql password and some things like that) to be able to use the bash script.
The tool creates a bash file in /tmp folder that contains all commands (rsync, mysql dump etc) to get the web, database and mail data from the source server.
The bash script also does a grep/replace in the transfered web files to change the path configurations from plesk-style to ispconfig.
If you want to use the current (very unstable) importer, please use the latest version from svn branch.